Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu

madhurikl has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by Illuminatus (Curate) on Apr 03, 2011 at 00:32 UTC
I have not personally used Net::SSH2:Channel, and the cpan documentation does not make it clear what the flag means for blocking. I would assume that 1 means blocking, but are you sure? You are not checking the results of any of the methods after the connect. However, if the auth was failing, I'm pretty sure the channel would return undef, so your first use of it would fail in an obvious way. Your example program is not displaying $len, so I'm assuming that in some previous incarnation, you printed it out. If you did not, and are going by the print statement for $output, then the read method could have failed. Have you compared the ssh2 library versions for the 2 remote systems? I would make sure I was using the same lib version on both before I checked anything else. fnord	[reply]
Re^2: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by madhurikl (Novice) on Apr 03, 2011 at 11:58 UTC
Hi fnord, I just didnt include the error handling stuff to make the question and the code simple to understand. a) The channel is successfully created. b) I tried with both blocking(0) and blocking(1). However, I need a blocking call, and as per my knowledge, blocking(1) sets the blocking. c) $len returns 0. I can see the number of bytes read because I have debug enabled. d) Yes. ssh2 library versions are same on both the ubuntu machine and the opensuse machine. I am also connecting to the same remote machine from both the systems.	[reply]
Re: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by syphilis (Archbishop) on Apr 03, 2011 at 00:46 UTC
Some questions: 1) Do the opensuse and ubuntu systems both execute commands on the same remote machine ? 2) Do the opensuse and ubuntu systems run the same version of Net::SSH2 ? 3) Is Net::SSH2 built against the same version of the libssh2 library ? 4) Do the opensuse and ubuntu systems both run the same version of perl ? On my Win32 machine (perl-5.12.0, Net-SSH2-0.33, libssh2-1.2.7) connecting to a linux server, your script runs fine. It also runs fine if I remove the ext_data() call - so try removing that line of code from your script and see if that makes any difference. Cheers, Rob	[reply]
Re^2: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by madhurikl (Novice) on Apr 03, 2011 at 12:04 UTC
Hi Rob, 1) Yes. Both execute same commands on the same remote machine. 2) Yes. Both run the same version of Net::SSH2 3) Yes. Both have the same libssh2 4) Yes. Both run the same perl 5.10.0 This is the debug output of my script : ------------ `libssh2_channel_open_ex(ss->session, pv_channel_type, len_channel_type +, window_size, packet_size, ((void *)0) , 0 ) -> 0x844420c Net::SSH2::Channel::read(size = 8192, ext = 0) - read 0 bytes - read 0 total output is status is 0 Net::SSH2::Channel::DESTROY Net::SSH2::DESTROY object 0x83aaa3c` [download]	[reply] [d/l]
Re^3: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by syphilis (Archbishop) on Apr 04, 2011 at 04:29 UTC
Sorry - only other idea I've got is to update the "problem" box to the latest Net::SSH2 and libssh2 (if that's not already the case) and hope that fixes it. And just try doing stuff until something happens that makes sense. Do you know if the sent command gets executed on the remote machine ? (I would guess that it does, and that it's only the output that gets lost, but it's something that should be verified.) Cheers, Rob	[reply]
Re: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by salva (Canon) on Apr 05, 2011 at 08:36 UTC
If you only need to run your program on Linux/Unix systems (no Windows), Net::OpenSSH may be a better option than Net::SSH2.	[reply]
Re^2: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by madhurikl (Novice) on Apr 08, 2011 at 09:45 UTC
I run on windows too using cygwin. And I am using Net::SSH2 because it is threadsafe, and I need to use threads.	[reply]
Re^3: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by Anonymous Monk on Apr 28, 2011 at 15:11 UTC
Here is the code I use under cygwin or linux redhat — # connect $ssh2->connect($remote_server) or die "\nERROR02 - Unable to connect H +ost $@ \n"; ($code, $error_name, $error_string) = $ssh2->error(); if ($code ne 0) { &log("error001","code = $code"); &log("error002","error_name = $error_name"); &log("error003","error_string = $error_string"); } if ($ssh_pattern eq '/passphrase/') { # authenticate with key and passphrase $ssh2->auth_publickey($remote_login, $pub_key_file, $priv_key_file +, $remote_password) or die "\nERROR03 Unable to login $@ \n"; ($code, $error_name, $error_string) = $ssh2->error(); if ($code ne 0) { &log("error011","code = $code"); &log("error012","error_name = $error_name"); &log("error013","error_string = $error_string"); } } else { # authenticate with user and password $ssh2->auth_password($remote_login,$remote_password) or die "\nERR +OR04 Unable to login $@ \n"; ($code, $error_name, $error_string) = $ssh2->error(); if ($code ne 0) { &log("error021","code = $code"); &log("error022","error_name = $error_name"); &log("error023","error_string = $error_string"); } } # DE-Block SSH2 for channel open (blocking to 1) $ssh2->blocking(1); # open channel 1 $chan1 = $ssh2->channel(); ($code, $error_name, $error_string) = $ssh2->error(); if ($code ne 0) { &log("error031","code = $code"); &log("error032","error_name = $error_name"); &log("error033","error_string = $error_string"); } # Block SSH2 for channel shell (blocking to 0) $ssh2->blocking(0); ($code, $error_name, $error_string) = $ssh2->error(); if ($code ne 0) { &log("error051","code = $code"); &log("error052","error_name = $error_name"); &log("error053","error_string = $error_string"); } # start channel shell $chan1->shell(); # send a CR to initialize the session print $chan1 "\n"; [download] Regards Charles.	[reply] [d/l]
Re^4: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by howheels (Initiate) on Nov 11, 2011 at 00:06 UTC
Re^3: Net::SSH2::Channel with exec, reads 0 bytes on suse while works fine on ubuntu by salva (Canon) on May 02, 2011 at 14:56 UTC
I have just released Net::OpenSSH::Compat::SSH2 that emulates Net::SSH2 on top of Net::OpenSSH. It is still a work in progress, but maybe it could solve your problem.	[reply]